Valves to control fluid flow are well known and are used in a variety of situations, including the control of water, natural gas, air, gasoline, and other fluids. A typical valve construction includes a main passageway through which the fluid passes, and a structure for interfering with the flow of the fluid. Exemplary of standard fluid valves are the gate valve, the needle valve and the ball valve. A gate valve includes a gate that is raised and lowered responsive to an external input to slow or stop the passage of fluid through the valve. The needle valve includes a stem that is moved against and away from an annular seat, thereby obstructing or permitting fluid to pass through the valve. A ball valve includes an internal ball that has a longitudinal bore through which the fluid passes. When the ball is rotated in either direction, the bore becomes transverse to the direction of fluid flow, slowing or stopping the passage of fluid through the valve depending on the degree of rotation.
Many valves are manually operated, and they therefore require that an operator be present to control the action of the valve. Under some circumstances, it may be desirable to operate the valve using an automated process, or to operate the valve from a remote source. Thus a valve may be opened and closed by an externally supplied electric current. However, in some environments, such as one where flammable materials are present, an externally supplied electric current of sufficient magnitude may be unreasonably dangerous due to the possibility of sparking. It is therefore desirable to provide a self-contained fluid valve that is light activated, and produces a low-power electrical input, resulting in an intrinsically safe fluid valve. There is also a need for a valve that is opened and closed using the fluid that the valve controls to activate the valve.